Intestinal Ischemia
Dheeraj Reddy
- Can affect small bowel ("mesenteric ischemia”) or large bowel (“colonic ischemia”)
- Onset may be gradual (atherosclerosis) or rapid (vascular occlusion or vasoconstriction)
Acute Mesenteric Ischemia | Ischemic Colitis |
|---|
| Small bowel | Large bowel |
| Abd pain early on, then abd tenderness later (“pain out of proportion”) | Abd tenderness > abd pain |
| Acute illness, afib, endocarditis | 90% patients are >60 y/o |
| BRBPR less common (>24 hrs after pain starts) | BRBPR onset < 24 hrs into pain episode |
| Dx: CT angio abd | Dx: colonoscopy |
Acute Mesenteric Ischemia
Pathophysiology
- Mesenteric arterial occlusion:
- Embolus originating in heart or aorta (i.e. valvular disease, AFib, AAA).
- Thrombus from mesenteric atherosclerosis (less commonly: abdominal trauma, infection, dissection).
- Mesenteric venous thrombosis:
- Associated w/ hypercoagulable states, prior surgery, abdominal mass; increased venous resistance leading to bowel wall edema.
- Non-occlusive mesenteric ischemia:
- Hypoperfusion due to mesenteric vasoconstriction (i.e. sepsis, pressors, low CO).
- Typically affects watershed areas (splenic flexure, rectosigmoid junction).
Presentation
- Early: Pain out of proportion to exam, severe abdominal pain initially WITHOUT abdominal tenderness.
- Late: Peritonitis/development of abdominal tenderness, distension, absent bowel sounds.
- May vary by etiology.
- Arterial occlusion: Sudden onset, severe periumbilical pain, nausea and emesis.
- Venous thrombosis: Gradually/insidiously onset, waxing and waning abdominal pain.
- Non-occlusive mesenteric ischemia: varies in location/severity; often overshadowed by precipitating disorder.
Evaluation
- Type and Screen, Lactate, BMP, CBC.
- KUB (low sensitivity).
- Ileus w/ distended bowel loops, bowel wall thickening, ± pneumatosis intestinalis (bowel wall air).
- Free intraperitoneal air --> immediate abdominal ex-lap.
- CTA A/P without oral contrast (obscures mesenteric vessels, ↓ bowel wall enhancement).
- Focal/segmental bowel wall thickening, intestinal pneumatosis.
- Portal vein gas, porto-mesenteric thrombosis.
- Mesenteric arterial calcification, mesenteric artery occlusion.
Management
- General: IVFs, NPO, hemodynamic monitoring and support (try to avoid vasoconstricting agents), anticoagulation, BSA, pain management.
- If peritonitis or perforation present, consult EGS.
- Mesenteric arterial embolism: Embolectomy vs. thrombolysis infused locally - Mesenteric arterial thrombosis: Surgical revascularization vs. thrombolysis + endovascular angioplasty/stenting.
- Venous thrombosis: Anticoagulation; possible thrombolysis if persistent symptoms.
- Non-occlusive: Treat underlying cause, stop vasoconstriction meds, consider intra-arterial vasodilator infusion.
Chronic Mesenteric Ischemia
Background
- Aka "intestinal angina”.
- Atherosclerosis of celiac or SMA is common but rarely consequential.
- Risk factors include smoking, diabetes, sedentary lifestyle, age.
- High-grade mesenteric vascular stenoses in at least two major vessels (celiac, SMA, or IMA).
Presentation
- Recurrent dull, crampy, abdominal pain <1hr postprandially; associated with food aversion and gradual weight loss
Evaluation
- - CTA A/P preferred (>90% sensitivity and specificity).
- - Can consider duplex U/S (NPV ~99%), though large habitus/prior surgery could limit utility.
Management
- Asymptomatic: Conservative management; smoking cessation/secondary prevention to limit disease progression, nutritional evaluation.
- Symptomatic: Revascularization (open vs. endovascular) to prevent future bowel infarction.
- 1st line is angioplasty/stenting.
- Open revascularization preferred for younger patients and those with re-stenosis.
Ischemic Colitis
Background
- Sudden, transient, nonocclusive reduction in blood flow to colon, typically at splenic flexure or rectosigmoid junction (“watershed” regions).
- Risk factors: Age (usually affects older patients), ACS, hemodialysis, shock, aortoiliac instrumentation, cardiopulmonary bypass, extreme exercise (marathon running).
Presentation
- Rapid onset, mild cramping abdominal pain, associated with urge to defecate, hematochezia.
- Tenderness (typically L. sided).
Evaluation
- Lactic acid (nonspecific but elevated), LDH, CPK, CBC (leukocytosis), BMP (metabolic acidosis).
- KUB
- CT A/P with IV contrast (and oral contrast if patient can tolerate).
- Consider CTA A/P if suspicion for vascular occlusion.
- Colonoscopy confirms diagnosis.
- Edematous, erythematous and friable mucosa interspersed pale areas.
- Bluish hemorrhagic nodules representing submucosal bleeding.
- Segmental distribution, abrupt transition between injured and non-injured mucosa.
Management
- General: IVFs, bowel rest, antibiotics (Zosyn vs. CTX/Flagyl)
Ischemic Colitis Management
| Classification | Management |
|---|
| Mild | No risk factors* | - Supportive care and observation
- Antibiotics can be stopped if no ulceration
|
| Moderate | 1-3 risk factors | - Same as mild ischemia if no vascular occlusion
- Systemic anticoagulation +/- vascular intervention if mesenteric occlusion
|
| Severe | > 3 risk factors, peritoneal signs, pneumatosis, pneumoperitoneum, gangrene or pancolonic ischemia on colonoscopy | Consult EGS for abdominal exploration and segmental resection |
